This invention relates generally to dentistry and, more particularly, to methods and apparatus for eliminating dental handpieces as a possible source of transmission of disease.
A significant concern exists that the dental operatory is a possible source of transmission of microbial disease, such as hepatitis B (serum hepatitis) and AIDS (acquired immune deficiency syndrome). Thus, it is thought that saliva may be a main vehicle for the transmission of such diseases and studies have shown that whereas the incidence of hepatitis B in the general population is 0.3%, up to 5% of the dental community has contracted a clinical infection. For this reason, sterilization and cleaning of dental instruments following each use is important to prevent microbial transmission to both dentists as well as to patients. Sterilization of dental instruments may be accomplished by any procedure that destroys a viral coat, including, for example, placement in 100.degree. C. water for about thirty minutes or autoclaving in 121.degree. C. steam at 15 psi for thirty minutes. The sterilization of dental hand instruments, such as probes, excavators, mouth mirrors, and forceps, has become routine.
The high-speed air-driven dental handpiece is a widely used dental instrument which is known to collect particulate matter and bacteria and may be a source of hepatitis or AIDS virus transmission. It has been conventional to disinfect high-speed handpieces by scrubbing with a detergent and wiping with alcohol after use. However, wiping may not remove all debris and short contact with disinfectant may not be sufficient for sterilization.
It has therefore been suggested that handpieces be designed so as to be autoclavable and that the handpiece should be sterilized by autoclaving after every use. However, studies have shown that this technique has drawbacks. For example, firstly, if autoclaving were to be routinely performed, several handpieces would be required for each operatory to account for turnaround time and malfunctions. Additional time for relubrication would also be required. For this reason, dentists may tend not to autoclave the handpieces. Secondly, autoclaving may not be effective in killing all microbes on and in the handpieces. Dried saliva and serum may protect organisms in the deep recesses of the handpiece. Lubrication oil covering the narrow internal parts of the handpieces shield spores from pressurized steam and acts as a protective flux. Studies have shown that the usual autoclaving schedules for downward deplacement sterilizers with fixed programs, commonly used in the dentist's office, are not sufficiently effective to give a probability of 10.sup.-6 or less of surviving microorganisms being present. Thirdly, some dental handpieces can be damaged by conventional sterilization procedures which can undermine the efficiency of rubber gaskets. Fourthly, studies have shown that performance of handpieces which are sterilized by autoclaving deteriorates over a period of time. Thus, the speed of the handpiece decreases over a period of time when subjected to periodic autoclaving. The water spray from autoclaved handpieces becomes course. Resistance in the chuck to inserting and removing burs increases.
In summary, the high speed handpiece is a weak link in the chain of disinfection or sterilization in the dental office. At the present time there is no standardized effective means for sterilizing a conventional high speed handpiece for routine use.